In U.S. Pat. No. 5,348,105 (Lappalainen) assigned to Tamrock Oy and issued Sep. 20, 1994 is disclosed a method for alignment of a drill mast in a drilling operation of the general type with which the present invention is concerned.
Typically a drilling machine includes a carrier vehicle movable on tracks over rough terrain and carrying a boom which can be rotated around a vertical axis or joint to left and right. At the end of the boom is mounted a mast for a drilling tool so that the angle of the mast defines the drilling direction. The mast is mounted on the boom for pivotal movement about two axes with respect to the vertical so that its position forward and rearwardly and its position side to side can be adjusted. Such a machine is commonly used in an excavation process.
In excavation, drilling is usually performed by drilling parallel holes side by side in a row where the holes lie in a common shearing plane which is generally perpendicular to the direction of excavation across the area to be excavated. The holes are then charged and blasting is carried out along the shear plane to extract rock in front of that shear plane.
In order to ensure that the excavation takes place in a desired manner, the drill holes have to be positioned sufficiently accurately in the shearing or excavation plane in question and in parallel with it as the excavation is designed to be performed in a predetermined order. Control and measuring devices are used to position the drilling machine of the rock drilling equipment in a desired direction with a desired inclination. Such devices indicate the angle of inclination of the mast of the drilling machine in two planes perpendicular to each other. For example, the angle can be indicated in a first vertical plane extending in the longitudinal direction of the boom and in a second vertical plane transverse to the end of the boom, so that the mast can be positioned at a desired angle with respect to the vehicle.
For the drilling process, the directional angles of the mast and thus those of the drill rod are calculated and determined as inclinations in the drilling direction. This is inconvenient and complicated, but there are aligning devices developed for indicating the direction of the mast and thus that of the drill rod in a desired manner with respect to the vehicle.
In the above patent there is shown a method which uses a reference direction along a sight line to a remote visible stationary target selected so that the target and thus the sight line is determinable in every drilling position of the vehicle in the alignment. An angle between the reference direction and the drilling direction is determined after the first drilling position of the drilling equipment on the basis of the reference direction. The angle between the longitudinal direction of the vehicle and the drilling direction is determined, and the mast is aligned on the basis of the angle so determined so that it is parallel with the drilling direction and the drilling plane.